The present invention relates generally to introducer sheaths and, more particularly, to a novel intravenous tube and valve assembly for use therewith.
It is well known to medically treat a patient by intravenously introducing fluids into an artery or vein. In this regard, an introducer sheath or hemostasis cannula assembly is generally provided, for example, similar to that disclosed in U.S. Pat. No. 4,000,739. As shown and described in this patent, the main body portion of the assembly has a tapered portion at the outlet side thereof within which is positioned a length of flexible tubing. The catheter is inserted into the assembly through the gasket assembly at the inlet side of the main body, whereby the gasket assembly provides a fluid-tight seal. After the catheter is in position, fluid may be injected through the catheter into the vascular system for treatment of the patient.
A problem with conventional flexible tubes used with introducer sheath assemblies is that the tube walls tend to collapse or kink when flexed, such as may occur when the patient moves, and flow reduction or stoppage may result. Recent developments have attempted to overcome this problem by utilizing a helical coiled spring as part of the flexible tube, for example, as shown in U.S. Pat. Nos. 3,618,613; 3,841,308; 3,963,856; 4,044,765; 4,052,989; 4,068,660; and 4,368,730. For related, but less relevant subject matter, see also U.S. Pat. Nos. 2,437,542; 2,472,483; 4,362,163; and 4,425,919. Generally, however, the formation of such inert plastic tubing with the helical coiled spring requires either that the plastic be heat shrunk or heat bonded to the spring or force fit with respect thereto. The problem with using a force fit or extrusion coating method is that, if the wire of the spring has an extremely small diameter, which is generally necessary, it cannot withstand the forces applied during such methods. In addition, the use of heat to cure the plastic material could not be used with a plastic spring since the coil itself would melt. Accordingly, it is generally necessary to provide relatively large gauge coils, thereby reducing the density of the coils and the kink resistance properties.
U.S. Pat. No. 4,044,765 discloses an outer tubular sheath formed of a heat-shrinkable material, while an inner coating or lining is deposited by a solution, emulsion or dispersion of the same type of inert plastic as that used for the outer sheath and which is dried or cured by heating the entire unit to about 250.degree. F. for about 10 minutes. The outer sheath, however, is still necessary in this patent for the purpose of forming a base on which the inner coating or lining can be formed. This patent also suffers from the deficiencies aforementioned since the solution must be cured by heating.
Although U.S. Pat. No. 3,618,613 does disclose curing by air drying, the patent still requires the use of an inner tubing to provide a base on which the outer coating can be formed. This results in force fitting of the spring over the inner tubing, which suffers from the disadvantages of providing undue forces on the spring and which also greatly increases the wall thickness, thereby lessening the kink resistance properties.
With respect to known hemostasis valves, U.S. Pat. No. 4,000,739 provides a pair of juxtaposed flexible gaskets mounted in the posterior end of the main body of the introducer sheath. The exteriorly positioned gasket of the pair is provided with a central opening which forms a seal around the catheter inserted therethrough, and the second interiorly positioned gasket is provided with a "Y" slit, the center of which is aligned with the axis of the central opening of the first gasket. The second gasket is compressed against the first gasket to seal the passage when the catheter is removed. A problem with such "Y" slit arrangement is that the slit extends through the second gasket generally in line with the longitudinal axis of the introducer sheath. As a result, when the catheter is inserted therethrough, back pressure from fluid within the introducer sheath may leak out through the slit; that is, the gaskets often do not form a complete seal against blood loss. See also U.S. Pat. No. 4,430,081. Other patents which are less relevant are U.S. Pat. Nos. 584,091; 3,620,500; 4,342,315; 4,405,316; 4,405,320; and 4,468,224.
U.S. Pat. No. 4,436,519 discloses an arrangement in which a single slit at the apex of a hemispherical projection of a gasket is provided through which the catheter is inserted. Because of the hemispherical outer surface of the projection, fluid back pressure tends to close the slit around the catheter and provide a fluid-tight seal. However, such construction is relatively complicated and also requires the use of reinforcing ribs about the hemispherical projection which further complicates the construction.